Production of olefin polymers



Oct, 22, 1946.V G. c. BAILEY lPRODUCTION OF OLEFIN POLYMERS .Filed Jan.30, 1942 ATTORN EY Patented Oct. 22, 1946 2,409,727 PRODUCTION OF OLEFIN`POLYMERS Grant C. Bailey, Bartlesville, Okla., assignor to PhillipsPetroleum Company, a corporation of Delaware Application January 3o,1942,seri1`N0.4'2s,966

5 Claims.

'Ihis invention relates to the catalytic polymerization of mono-olens,and more particularly tothe production of tetra-isobutylene fromisobutylene and di-isobutylene.

Tetra-isobutylene is a mono-oleiin containing 16 carbon atoms permolecule. Tetra-isobutylene exists in several isomericY forms possessinghighly branched carbon structures and each structure possesses an activeolefinic bond making it useful in the preparation of chemicalderivatives of this particular olen species through various'reactionprocedures. Hydrogenated tetraisobutylene possesses a high octanenumber, making it useful as fuel of very low volatilityininternal-combustion engines. It has a solidiiying temperature below100 C., making it useful at very low temperatures as a hydraulic fluid,for example. In many such applications, it is desirable to usea producthaving a particular molecular weight and boiling range, together withunique characteristics as previously suggested; tetra-isobutylene isespecially suited for some of these applications.

The catalytic polymerization of mono-olens to higher-molecular-weightproducts is Well known. Isobutylene is one of the most reactivemono-olefins, and its polymerization using various catalysts andconditions and its polymerization products have been the subjects ofmany investigations.V These products range from di-isobutylene, which isin the boiling range of gasoline, through oils, to viscous, rubber-like,and nonelastic resinous products. In any given reaction, the productusually contains a series of polymers of different molecularn Weights,each successive chance in molecular weight corresponding to one moleculeof monomer. The average molecular weight of a polymer'product dependsupon the catalyst and the polymerization conditions. Us-

ing highly active catalysts, such as aluminum chloride, the proportionof products of different molecular Weights follows a probabilitydistribution around the average molecular weight. In such cases theaverage molecular weight is a function of the temperature ofpolymerization, the lower the temperature the higher the averagemolecular weight.

In manycases where the polymerization catalyst is less active, such aprobability distribution is not found. The rates of the formation ofvarious polymeric `formsmay vary so greatly with temperature that trueequilibrium conditions are never attained and the composition of theproduct depends upon the comparative rates of the competing reactions.

(Cl. 26o-683.15)

In the direct polymerization of an olen to a polymer having a desiredmolecular Weight, such as the polymerization of isobutylene totetra-isobutylene, for example, polymers of both higher and lowermolecular weight are formed. For any given catalysts,V conditions can befound which give an optimum yield of the desired polymer, but the higherand lower polymers Will be present in lesser, but substantial amounts.

` This is illustrated by the data in Table I, which gives the productanalysis of the liquid obtained from a run in which gaseous isobutylenewas polymerized over activated fioridin at room teinperature.

` Table I Component:` Per cent of total liquid Di-isobutylene 17Tri-isobutylene 50 Tetra-isobutylene 17 Penta-isobutylene 5Hexa-isobutylene 1 Hepta-isobutylene 0.5 Residue 9.5

Orthophosphoric acid also readily polymerizes isobutylene. The productvwhich was obtained when isobutylene was polymerized with orthophosphoricacid at 30 C. comprised essentially diand tri-isobutylene, while at 130C. seven isomeric polymers were produced.

Sulfuric acid readily brings about the poly- .merization of isobutyleneto products containing di-isobutylene, tri-isobutylene, and higherpolymers. At relatively low temperatures and loW acidv concentrations,relatively high proportions of dimer are produced. As the temperatureand acid concentration are increased, the proportion ofhigher-molecular-weight polymers, trimer and tetramer especially, andthe complexity of the polymer are increased. At still highertemperatures, the average molecular weight oi the product decreases, asa result of extensive changes in the hydrocarbons during polymerization.

Metal halide catalysts, such as aluminum chloride, boron fluoride, andthe like, are very active, bringing about the rapid polymerization ofisobutylene to relatively high-molecular-weight compounds. Attemperatures of to 100 C.,

isobutylene is converted to resinous or plastic polymers of very highmolecular weight. At 80 C.,`the polymer product contains oleiins rangingfrom gasoline to lubricating oils, or dimers to decamers and sometimeshigher. With increase 3 in temperature of reaction, there is produced adecrease in the average molecular weight of the product and an increasein the complexity of the polymer or in the other reactions accompanyingsimple polymerization.

In all such catalytic polymerization systems, one polymer is oftenproduced in somewhat higher proportion, but always with substantialamounts of polymers of higher and lower molecular weights accompanyingit, The preparation of a product containing only trimer or only tetrameris thus not'possible in the conventional polymerization system. However,it has been found possible by proper selection of 'a catalyst and areaction system to limit markedly the reaction so that dimer alone isproduced in high concentration.

Two factors contribute tohi'gh maximum yields of dimers as contrasted tothe lower maximum yields of any higher-molecular-weight product.Firstly, there is no polymer having a molecular weight lower than thedesired product. 'Secondly, the conversion Vto each successivelyhighermolecular-weight vpolymer requires greater catajlyst activity thanthe previous conversion. Therefore, careful 'selection of catalyst andconditions minimizes the'formation of 'higher polymers. Severalcombinations of catalysts and conditions have been found by variousworkers whereby di-'isobutylene can be prepared from iso- `butylene inyields of 80%-01 greater.

I have 'now found that `di-isobutylene can 'be converted'totetra-isobutylene in high yields using 4phosphorus pentoxide as 'acatalyst. This invention affords a method of converting isobutylene totetra-isobutylene in high yields and more `readilythari was previouslypossible. This is accomplished by using a two-step process comprisingpolymerizing isobutylene to di-isobutylene under conditions that producehigh yields of diisobutylene, separating this dimer from other productsand converting it to tetra-isobutylene 'usingrphosphorus pentoxide ascatalyst.

It is an object of my invention to convert'a low- `boiling oln to ahigher-boiling olefin. Another object of my invention is to produce anolefin polymer having a desired molecular 'weight in high yields romanolen'of Vlower'molecul'a'r weight.

fAno'the'r object is to rapidly polymerize a mono-olen to a lpolymer ofdesired molecular vweight 'in high yields.

Another object is to produce high yields of tetra-isobutylene.

Further objects and advantages of my invention willbe apparent fromtheaccompanying disclosure.

My invention'will now be more particularly described and 'exempliiied inconnection with the drawing'which is a schematic flow-diagramillustrating specific embodiments of theinvention Vfor the production ofhigh yields of desired polymeric hydrocarbons lfrom monomerichydrocarbons.

Isobutylene, or a 'hydrocarbon mixture containingessentially'isobutyle'ne and other hydrocarbons substantially inertunder theconditions at which isobutylene is subsequently converted,is'passe'dthrough conduit ll controlled by valve IU to polymerizationunit l2, wherein isobutylene is 'treated yaccording to any of theprocesses'well known in the art for the production therefrom ofdi-isobutylene in optimum yieldswith only small amounts of otherpolymeric hydrocarbons being produced. Sulfuric acid having a strengthbetween 60 and 75per cent is a particularlyadvantageous-catalyst'for'such a conversion. Sulfuric acid of suchstrength can be used to selectively absorb isobutylene from a mixture ofnormally gaseous hydrocarbons. Upon heating such a sulfuric acid extractto about 100 C., isobutylene is polymerized to a product containing 80per cent or more di-isobutylene. When the hydrocarbon stock chargedthrough conduit H is rich in isobutylene, treatment in polymerizationunit l2 with sulfuric acid as described will convert isobutylene to aproduct containing more than 90 per cent di-isobutylene.

I have round that good yields of di-isobutylene can also be obtainedfrom isobutylene by treating an isobutyle'ne-containing mixture withphosphorus pentoxide catalyst in the ytemperature range of about -5 to+15 C. and preferably from (l to 10 C. As-the temperature is decreasedbelow 5 C., the rate of polymerization of isobu'tylene to di-isobutylenedecreases very rapidly, and as the temperature of polymerization isincreased above 15 C., the proportion of dimer in the Iproduct decreasesrapidly, trimer becoming the main product. Using polymerizationtemperatures in the range of 0 to 10 C., 50 to'60 per cent yields ofdl-isobutylene can be obtained.

Eluent from polymerization unit E2 is passed through conduit 3controlled by valve -35 to separator id. Any unreacted isobutylene inthe efiuent from unit 'l 2 is separated therefrom in separator i5 andpassed through conduit l5 controlled by valve S6 toconduit AIl andthence to polymerization unit l2. When material lowerboiling 'thanisobutylene is charged to my process through conduit VH and issubstantially inert under the conditions `in unit I2, such material isremoved from'separator 'ifi and from my process through conduitsfbll andi6 controlled by valve 3l. When 'it is desirable to have such materialpresent during the conversion of isobutylene in unit i2, 'it can berecycled from separator I4 through conduits "54 and l5 controlled byvalve 38, whenvalve v3'! inconduit lis wholly orpartly closed.Tri-isobutylene produced in unit `I2 is removed from separator Ylilthrough conduit 58 controlled by valve 63 andmay be lfurther treated `asappears desirable. Usually I prefer to pass such `trimer material todepolymerization unit |9, the operation of which is subsequentlydescribed. -Sometimes minor amounts of tetra- 4isobut'yleneare alsoAproduced'in unit l2 and such material lmay be removed from separator I4through `conduit "Se controlled by valve fS5 as a desirable product ofmy process.

Polymeric `Vhydrocarbons boiling above the tetra-isobutylene range `areremoved from separator |11 throughconduit l? andywhen such maerial isconsidered as undesirable in my process, it can be removed therefromthrough conduit I8 controlled by valve 39. When, however, suchhigh-boiling polymeric hydrocarbons can be depolymerized to usefulmaterials, for example, they are passedthrough valve ll'in conduit kI'lto depolymerization unit I9 when valve '39 in conduit I3 is 'wholly or`partly closed. In unit i9 such polymers along with any trimer ortetramer passed thereto are depolymerized under suitable conditions oftemperature, pressure, and'reaction time, in the presence or absence ofcatalytic materials for .promoting depolymerization Vreactions toproduce monomeric olens that can be advantageously used, such Vasisobutylene, tetraisobutylene and even olen hydrocarbon polymers in thelubricating-oil range. The depolymerization of high-molecular-weightole- 1in polymers to lower-molecular-weight hydropolymerization unit l2will be quite small, and all such material may be charged to the depoly`merization. Y

Eflluent from the depolymerization unit `I9 is passed through conduit6E) controlled by valve 59 to separator 55. Inseparator 55ianylow-boiling material having less than four carbon atoms per molecule isremoved from the system through conduit 56 controlled byvalve 51.Usually the amount of this material will be very small and generallynegligible. Isobutylene contained in the effluent from unit i9'i's'passed from separator 55 through conduit 2| controlled by valve 43to conduit Il wherein it is admixed with fresh charge stock topolymerization unit I2. A di-isobutylene fraction, which will sometimesconstitute an appreciable portion of the eflluent from depolymerizationunit .l9,'is -removed from separator 55 through conduit 22 and passedthrough valve 48 to conduit 24 and thence through valve 4l. topolymerization unit 25 subsequently described herein, f

Any hydrocarbon material having a higher boiling range thandi-isobutylene and including material in the lube-oil boiling rangewisremoved from separator 55 through conduit 20 y,controlled byva'lve42.""Materialboiling abovethe lube-oil range', including tars" andhigh boilingundepolymerized material from unit i9, is removed fromseparator 55 through conduits 63 controlled by valve 58. Insomevinstances it will be. desirable vto return material `removedthrough conduits 20V and/or 53 to the depolymerization.unit |91for.conversion to additional quantities of di-isobuty-` lene, eitherdirectly or indirectly, by means not..

shown inthe drawing. Such operation is particularly advantageous when-itis desirable` to charge as much di-isobutylenetoV polymerization unit 25as possible. l

In polymerization0 unit pentoxide under conditions for the, productionbfoptimum yields of tetra-isobutylene as disclosed herein. In someinstances it will be desirable to charge di-isobutylene to my processfrom some` appreciable conversion, of said hydrocarboncharge. Inunit v25phosphorus pentoxide is contacted with di-isobutylene charged, theretoina temperature range between about 0 C. and*4 100A C. and underv asuiiicient pressure that the hydrocarbon charge will be in the liquidphaser, Within this temperature range the reaction is essentiallydimerization of diisobutylene. vNo polymers higher-boilingthantetra-.isobutylene are usually found in the product. Although thepolymerization reaction in unit 25 ,proceeds more `rapidlyat'highertemperatures arange between aboutZO" C. and 60 C. is usuallypreferred. 'Atsubstantially .fpure di-,isobutylene is` contacted withphosphorus.

It may, however, be admixedwith` high purity since no isododecene oriso-eicosene` is produced by the polymerization in 25,1.

mospheric pressure is usuallypreferred in operationsi of this kind atthe lower temperatures, althoughhigher pressures can be used to advanl-jtageand pressures as high as 1000 pounds per4 square inch gage producedesirable results. The reaction time for carrying out this`polymerization step is -preferably in the range between three hoursJand seven hours although reactionptimes outside of this range have beenfound toV produce substantial amounts of the desired product. When shortreaction times are employed in unit 25 at any giventemperature Withinthe range disclosed, less di-isobutylene is polymerizedper pass and,therefore, more di-isobutylene is recycled to unit 25 for furtherconversion to tetraisObutylene. Long reaction times in unit 25 favorhigher conversion per pass operation Vwith an inherent less amount ofrecycle of unpolymerized di-isobutylene to unit 25. However, prolongedcatalyst life and other factors may make it desirable'to work with shortreaction times and less polymerization per pass. i

In unit 25 it is desirable to secure intimate. contact between thephosphorus pentoxide .catalyst and hydrocarbon material.` To facilitateintimate `mixing,fmaterials which aid in dispers? ing the phosphoruspentoxide may be used, such as sand or lamp black. Efficient contactbetween catalyst and reactants is highly important in the`polymerization step in unit 25.

. The di-isobutylene charged to polymerization unit 25 is preferablyquite pure and particularly free from oxygen-containing compounds, suchas are readily formed when di-sobutylene is eX- posed to air or oxygen.The presence of oXygen-containing compounds in the di-isobutylenev feedto unit 25 greatly decreases the rate of polymerization therein andnecessitates the use of larger quantities of phosphorus pentoXidecatalyst to produce satisfactory yields than whensuchu'oxygen-containing compounds are absent from unit 25.

Under the more favorable conditions discussed herein the phosphoruspentoxide catalyst is not rapidly deactivated. The useful life of thecatalyst depends `upon the rate at which it is deactivated by absorptionof water and the rate at which sludge-like materials are built up byreac-V tion with oxidized olefins or other reactive impurities. A

:Effluent from polymerization unit 25 is passed through conduit 2l.controlled by valve 451:0 separator` 28. Phosphorus pentoxide `catalystis removed from the-liquid by filtration, centrifuging, or any othersuitable means well known to the art, and is then recycled topolymerization unit 25 by conduit 30 controlled by valve 46. When usedcatalyst has become so spent as to be uneconomical for conversion ofadditional di-iso butylene, such spent material or spent catalyst isremoved from my process through conduit 3l controlled by valve 52whereafter it may be disposed of or treated as appears desirable.Usually suchspent material is regenerated to active catalytic materialand recharged to unit 25 and/ or toany other catalytic process or unitemploying phosphorus pentoxide as a catalyst. Unreacted dpi-isobutyleneis separated and recycled to polymerization unit 25 through line 29controlled by valve 49. Desired tetra-isobutylene is removed fromseparator 28 through conduit 33 controlled by valve 50. It is readilyobtained in a state of thereby affording a simple separa-tion insepara-i tor 28; During an extended operation of my process smallamounts of polymeric material higher boiling than tetra-isobutylenemaybe produced inunit 2-5 and can be removed from separator 28 throughconduit 32 and from my process through valve 5|. When such material iseasily depolymerizable to a-lower-molecular-weight polymer such asdi-isobutylene, or to isobutylene, it is preferably charged todepolymerization unit I9wherein a conversion is carried out as describedherein.

My invention is furtherillustrated by the following examples which arerecorded to disclose specific applications of my invention and are notintended to limit unnecessarily the scope or utility of the principlesof my invention in anyway.

EXAMPLE y I A steel pressure autoclave which was equipped with aneicient stirrer and an internal thermocouple was thoroughly cleaned anddried using a stream of dried nitrogen. Phosphorus pentoxide wasintroduced into the autoclave under anhydrous conditions. A charge stockconsisting of 76 per cent isobutylene and 24 per cent isobutane wasforced into the autoclave during a 5-hour period. The autoclave wascooled with ice, and the charging rate adjusted so that the internaltemperature was held between 0 and 2 C. The unreacted isobutylene andisobutane were released from the reactor, and the polymer productfiltered and fractionated. The product hadv the following composition:

Table Il Component: Volume per cent Di-isobutylene 58 Tri-isobutylene 17Tetra-isobutylene 'I Higher polymers 18 100 EXAMPLE IIy The run cited inExample I was repeated except the temperature of the reaction was heldat about 35 C. Fractionation of thev product showed it to have thefollowing composition:

Table III Component: Volume 17ery cent Di-isobutylene 20 Tri-isobutylene60 Higher polymersl 20y EXAMPLE III 'Iwenty parts by weighty ofvdi-isobutylene and l 'part phosphorus pentoxide were agitated at lll-'-159C. for seven hours. The catalyst was removed by ltration, anddistillation of the product showed it to have the following composition:

Table IV Volume per cent Di-isobutylene 16 Tetra-isobutylene 84` EXAMPLEIV Twenty parts by weight of di-isobutylene andl part phosphoruspentoxide were contacted at 100." C. for 3 hours. The material wascooled, filtered and distilled. The liquid. product had the followingcomposition:

Table V Volume per cent Di-isobutylene 50 Tetra-isobutylene 50 ExamplesIII and IV show that phosphorus pentoxideA polymerizes di-isobutylene totetra-isobutylene over a wide range of temperature and that the reactionproceeds more rapidly at higher temperatures than at lower.

EXAMPLE V Twenty parts by weight of freshly prepared diisobutylene and 1part phosphorus pentoxide were agitated at room temperature for 4 hours.The product was filtered and distilled. The following composition wasfound:

Table VI Volume per cent Di-isobutylene 25 Tetra-isobutylene EXAMPLE VIThe run cited in Example V was repeated using di-isobutylene which hadbecome partially oxidized by contact with air. The product had thefollowing composition:

Table VII Component: Volume per cent Dl-isobutylene 96 Tetra-isobutylene4 Examples V and VI show that, in order to produce high yields oftetraisobutylene from diisobutylene using phosphorus pentoxide, thediisobutylene must be substantially free from oxidation products.

`various polymerizationu steps may be operated continuously orintermittently in batches as may be found most desirable for anyparticular case and-f the particular conditions used. The drawing is,ofcourse, diagrammatic and the application y of my invention on acommercial scale will necessitate the use of much equipment such aspumps, heaters, coolers, fractionators, and the like not shown in detailbut. which may be readily applied and'adapted for any particularinstallation by one skilledin the` art. separators, such as I4 and 28,willv advantageously comprise several individual units such as lters,fractional distillation columns, strippers, accumulators and the likeequipment well known in the separating art. The general process andpossible material flows have been disclosed and this together with thespecific examples are .believed tok be suicient to Serve as efficientguides.

I claim:

l; A process for producing high-boiling hydrocarbons from lower-boilinghydrocarbons, which comprises passing di-isobutylene to a polymerizationzone and contacting said di-isobutylene in the liquid phase in said zonewith phosphorus pentoxide at a temperature between 0 C. and

100 C. for a period of time such that an optimum amount oftetra-isobutylene is produced.

2. The process of claim 1 wherein the reaction time for thepolymerization is between three and seven hours.

3. In a process for producing high-boiling hydrobar-bons fromlower-boiling hydrocarbons, the steps which comprise passingdi-isobutylene to a polymerization zone, contacting said di-isobutylenein the liquid phase in said zone with phosphorus pentoxide at atemperature between C. and 100 C. for a period of time such as anoptimum amount of tetra-isobutylene is produced, passing eiuent fromsaid polymerization zone to a separating means, separating therefrom afraction rich in di-isobutylene and returning said fraction to thepolymerization zone, separating also therefrom a fraction comprisingessentially tetra-isobutylene, and removing said fraction from theprocess.

4. A process for the production of tetra-isobutylene by polymerizationof di-isobutylene Without the formation of substantial amounts oftri-isobutylene, Which comprises subjecting diisobutylene in the liquidphase to the action of phosphorus pentoxide at a temperature within therange oi approximately 0 C. to approximately 100 C.

5. A process for the production of tetra-isobutylene by polymerizationof di-isobutylene without the formation of substantial amounts oftri-isobutylene, which comprises subjecting diisobutylene in the liquidphase to the action of phosphorus pentoxide at a temperature within therange of approximately to approximately C.

GRANT C. BAILEY.

